Rob in your case an ACT Extreme PP and 6 puck disk should hold. Mine started slipping mainly due to it being a 10 year old pp that had a decent amount of wear on it. It didnt start slipping till I went up to 30psi and tried to do 2nd gear burnouts before the drag passes.
But again I think that was more to age than anything else. Other than that, the disks have always lasted, never popped a spring and for a 10 year old pp it still held pretty good and I was at 400+wtq at 30psi of boost, probably closer to around 450-470 I was at 391wtq on 24psi and stock intake manifold.
Id say give the ACT a shot, Im sure it will hold